1720665064721 has 2 divisors, whose sum is σ = 1720665064722. Its totient is φ = 1720665064720.

The previous prime is 1720665064717. The next prime is 1720665064817. The reversal of 1720665064721 is 1274605660271.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1427021376400 + 293643688321 = 1194580^2 + 541889^2 .

It is a cyclic number.

It is not a de Polignac number, because 1720665064721 - 2² = 1720665064717 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1720665064421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 860332532360 + 860332532361.

It is an arithmetic number, because the mean of its divisors is an integer number (860332532361).

Almost surely, 2^{1720665064721} is an apocalyptic number.

It is an amenable number.

1720665064721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1720665064721 is an equidigital number, since it uses as much as digits as its factorization.

1720665064721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 846720, while the sum is 47.

The spelling of 1720665064721 in words is "one trillion, seven hundred twenty billion, six hundred sixty-five million, sixty-four thousand, seven hundred twenty-one".